[Construction of Nalm6-Cas9 Cell Line for Genome-Wide Translocation Sequencing].

OBJECTIVE: In order to conduct high-throughput genome-wide translocation sequencing based on CRISPR/Cas9, Nalm6-cas9 monoclonal cell line expressing Cas9 protein was constructed by lentivirus transduction. METHODS: Lentiviral vectors LentiCas9-Blast, pSPAX2, and pMD2.G were used to co-transfect HEK293T cells to obtain recombinant lentivirus. After Nalm6 cells were infected with the recombinant lentivirus, the cells were screened by Blasticidin, and multiple monoclonal cell lines expressing Cas9 protein were obtained by limited dilution. Western blot was used to detect the expression level of Cas9 protein in monoclonal cell lines, and cell count analysis was used to detect the proliferation activity of monoclonal cell lines. LentiCRISPRV2GFP-Δcas9, LentiCRISPRV2GFP-Δcas9-AF4, LentiCRISPRV2GFP-Δ cas9-MLL plasmids were constructed, and transfected with pSPAX2 and pMD2.G, respectively. T vector cloning was used to detect the function of Cas9 protein in Nalm6-Cas9 monoclonal cell line infected with virus. RESULTS: Western blot showed that Nalm6-Cas9_1-6 monoclonal cell line had high expression of Cas9 protein. Cell count analysis showed that high expression of Cas9 protein in Nalm6-Cas9_1-6 monoclonal cell line did not affect cell proliferation activity. The Nalm6-Cas9_1-6 monoclonal cell line had high cleavage activity, and the editing efficiency of AF4 and MLL genes was more than 90% which was determined by T vector cloning. CONCLUSION: Nalm6-Cas9_1-6 monoclonal cell line stably expressing highly active Cas9 protein was obtained, which provided a basis for exploring the translocation of MLL in therapy-related leukemias based on CRISPR/Cas9 genome-wide high-throughput genome-wide translocation sequencing.

[Expression and Significance of BLIMP-1 in Regulatory T Cells of Children with Aplastic Anemia].

OBJECTIVE: To study the expression of B lymphocyte-induced mature protein-1 (BLIMP-1) in regulatory T cells (Tregs) of children with aplastic anemia (AA), and analyze its correlation with the number of Tregs and the levels of inhibitory cytokines interleukin (IL)-10 and transforming growth factor (TGF)-ß in plasma. METHODS: The peripheral blood samples of 10 newly diagnosed AA children and 10 healthy children were collected for experiment. qPCR was used to detect FOXP3 and PRDM1 mRNA expression levels. Flow cytometry was used to detect the proportion of Tregs, the expression of BLIMP-1 in Tregs, and the levels of cytokines such as IL-2, IL-17A, IL-6, interferon (IFN)-γ, IL-10 and TGF-ß in plasma. Pearson correlation model was used to evaluate the relationship between the expression of BLIMP-1 in Treg and the number of Tregs, as well as the levels of IL-10 and TGF-ß in plasma. RESULTS: Compared with control group, the proportion of Tregs in peripheral blood of AA children was decreased significantly (P<0.001); The plasma levels of proinflammatory cytokines IL-2, IL-6 and IFN-γ in AA children were increased significantly (P=0.033, P=0.031, P=0.006), and IL-17A also was increased but the difference was not statistically significant (P=0.052), while anti-inflammatory cytokines IL-10 and TGF-ß were significantly reduced (P=0.048, P=0.002). The relative expressions level of FOXP3 and PRDM1 mRNA in AA children were significantly lower than those in control group (P=0.037, P=0.016). The expression of BLIMP-1 protein in Tregs of AA children was significantly lower than that in control group (P<0.001). The expression level of BLIMP-1 protein in Tregs was positively correlated with the percentage of Tregs in lymphocytes (r=0.671, P=0.001), and was also positively correlated with the levels of IL-10 and TGF-ß in plasma (r=0.500, P=0.029; r=0.486, P=0.030). CONCLUSION: The expression of BLIMP-1 in Tregs of AA children is impaired, and the low expression of BLIMP-1 is related to the decrease of the number in Tregs and IL-10 and TGF-ß expressions.

Evolution of unconditional dispersal in periodic environments.

Organisms modulate their fitness in heterogeneous environments by dispersing. Prior work shows that there is selection against 'unconditional' dispersal in spatially heterogeneous environments. 'Unconditional' means individuals disperse at a rate independent of their location. We prove that if within-patch fitness varies spatially and between two values temporally, then there is selection for unconditional dispersal: any evolutionarily stable strategy (ESS) or evolutionarily stable coalition (ESC) includes a dispersive phenotype. Moreover, at this ESS or ESC, there is at least one sink patch (i.e. geometric mean of fitness less than one) and no sources patches (i.e. geometric mean of fitness greater than one). These results coupled with simulations suggest that spatial-temporal heterogeneity is due to abiotic forcing result in either an ESS with a dispersive phenotype or an ESC with sedentary and dispersive phenotypes. In contrast, the spatial-temporal heterogeneity due to biotic interactions can select for higher dispersal rates that ultimately spatially synchronize population dynamics.

Studying genetic code by a matrix approach.

Following Petoukhov and his collaborators, we use two length n zero-one sequences, alpha and beta, to represent a length n genetic sequence (alpha/beta) so that the columns of (alpha/beta) have the following correspondence with the nucleotides: C ~ (0/0), U ~ (1/0), G ~ (1/1), A ~ (0/1). Using the Gray code ordering to arrange alpha and beta, we build a 2(n) x 2(n) matrix C(n) including all the 4(n) length n genetic sequences. Furthermore, we use the Hamming distance of alpha and beta to construct a 2(n) x 2(n) matrix D(n). We explore structures of these matrices, refine the results in earlier papers, and propose new directions for further research.

Applications of Perron-Frobenius theory to population dynamics.

By the use of Perron-Frobenius theory, simple proofs are given of the Fundamental Theorem of Demography and of a theorem of Cushing and Yicang on the net reproductive rate occurring in matrix models of population dynamics. The latter result, which is closely related to the Stein-Rosenberg theorem in numerical linear algebra, is further refined with some additional nonnegative matrix theory. When the fertility matrix is scaled by the net reproductive rate, the growth rate of the model is $1$. More generally, we show how to achieve a given growth rate for the model by scaling the fertility matrix. Demographic interpretations of the results are given.